DESCRIPTION (from the application): Aggregation of Beta-amyloid (ABeta) peptides is now widely believed to play a central role m the pathogenesis of Alzheimer's disease (AD). ABeta peptides are generated within neurons by the regulated cleavage of the Beta-amyloid precursor protein (BAPP), but the molecular mechanism by which ABeta causes disease remains uncertain. Over the past decade, the Program Project has investigated the regulation of BetaAPP metabolism by protein phosphorylationdependent signal transduction pathways. The major goal of this project is to better understand the molecular mechanisms that control the regulated cleavage of BetaAPP and the levels of intracellular and extracellular ABeta. We have investigated several systemic hormones that decline with aging and have been associated with the development of AD, including estrogen, testosterone and insulin. Estrogen replacement therapy in postmenopausal women was reported to be protective for the development of AD, and we demonstrated that estrogen affects BetaAPP metabolism and ABeta secretion in cultured neurons. Testosterone declines with aging in both men and women, and we reported that testosterone also reduces neuronal ABeta secretion. Increasing evidence indicates that insulin has important signaling functions in the brain and that diabetes mellitus is a risk factor for AD. We found that insulin regulates the intracellular and extracellular levels of (ABeta) in neurons, and since the pathways for insulin signal transduction art especially well established, we propose to investigate how insulin effects ABeta. We propose to identify the specific hormone receptors and signal transduction pathways that mediate the effects of gonadal hormones or insulin respectively, on the intracellular and extracellular levels of Abeta40 and Abeta42, and to assess whether gonadal hormones and/or insulin can affect ABeta plaque deposition or the subcellular localization of ABeta40/42 in transgenic mouse models of AD. We plan to utilize cultured primary neurons, specific inhibitors and cell lines expressing mutated construct: of known gonadal hormone- or insulin-relevant signal transduction components and kinases, and transgenic mice, to investigate the effects of gonadal hormones and insulin on BetaAPP metabolism, the intracellular and extracellular: levels of ABeta, and ABeta neuropathology. The ultimate aim of this study is the development of more effective molecular. based treatment strategies for AD.